Well known in the art is a stencil printing device in which a perforated stencil sheet is wound around a circumferential surface of a printing drum with an ink supplied thereto, and in which the ink is transferred from the printing drum to a printing sheet through the perforated stencil sheet by pressing the printing sheet to the printing drum while the drum is rotated.
In a stencil printing above, it has been proposed in Japanese patent laid open publication (Kokai) No. 62-127276 that printing density of an image to be printed on a printing sheet is variably set by variably setting a pressing force to be applied to the printing sheet against the printing drum, in accordance with printing density information given by a means for setting printing density information, for instance, a printing density set up key provided on an operation panel.
Furthermore, since the printing density in stencil printing changes with printing speed, Japanese patent laid open publication (Kokai) No. 06-155880 has already proposed a method for implementing stencil printing at a desired density irrespective of the change in printing speed. This method comprises variably setting a pressing force applied to the printing sheet against the printing drum, in accordance with printing speed information given by a means for setting printing speed information, for instance, a printing speed set up key provided on an operation panel.
With recent diversification in quality of printing paper and originals, there is a demand on a stencil printing device which can more widely and finely control printing density. However, because no index for controlling printing density has been clarified, such a demand could only be satisfied by collecting voluminous data on combinations of a rotation speed of a printing drum and a corresponding pressing force applied to a printing sheet with respect to various printing densities. Thus, it was practically unfeasible to load the entire data into a stencil printing device to control printing density.